The invention relates to a device for reading information from a magnetic recording medium, which device comprises a transducing element and a magnetic yoke co-operating with the transducing element and being provided with a first flux guide and a second flux guide spatially separated locally therefrom, said device also having a face for magnetic flux coupling of the transducing element with the magnetic recording medium. A device of this type is known from U.S. Pat. No. 4,489,357 (herein incorporated by reference).
Devices for reading information from a magnetic recording medium are generally known and their use is still increasing as a result of novel magnetic recording systems, particularly those relating to computer applications, video applications and digital audio applications. The recording medium may have the shape of a magnetic disc, a drum or a tape, or any other magnetic body which is capable of receiving and storing data with a high density. Whatever type of magnetic medium is used, it will always be necessary to use a device for recording information in the medium and a device for reading this information when necessary. These devices have been developed in a wide variety of designs, and the known devices for reading information can in principle be divided into two types, namely the devices of the inductive type provided with an inductive element particularly an electric coil, and the devices of the magneto-resistive type provided with a magneto resistive element.
An example of the first-mentioned type is shown in the form of an inductive magnetic head for vertical recording in Netherlands Patent Application No. 8,303,023 and an example of the last-mentioned type is shown in the form of a thin-film read head in U.S. Pat. No. 4,489,357. The thin-film magnetic head known from U.S. Pat. No. 4,489,357 has an elongated magnetoresistive element bridging a gap located between two co-planar magnetically permeable layers and is provided at two facing ends with contacts for connection to a measuring current source.
It is to be noted that the sensitivity of inductive read heads is limited, at low frequencies, because the output voltage across the coil ends is slow due to the proportionality of the voltage with the time derivative of the changing flux threading the coil. This problem cannot be solved by using a coil having a large number of turns, because such a coil is largely impracticable from a technological point of view and, moreover, the resistance of the coil would increase drastically so that thermal noise would be a problem.
As is assumed to be known, magnetoresistive read heads supply an output voltage which is proportional to the flux applied to the magnetoresistive element. Therefore, these heads are very sensitive at low frequencies. A drawback of the magnetoresistive read heads is their low magnetic efficiency due to the high magnetoresistance which is caused, inter alia, by the thin magnetoresistive element. Another drawback of the magnetoresistive read heads is that these heads have a rather high interference level due to the occurence of the so-called Barkhausen effect which relates, inter alia, to the interaction between the magnetoresistive element and the flux guides. More information on these aspects can be found, for example in the Article "The effect of lamimating permalloy flux guides in a thin film magnetic recording head" by J.A.C. van Ooijen; Europhysics Conference Abstracts, soft Magnetic Materials 5, 1981, pages 131, 132.